How to add authorization to a Flask application

Robust and reliable authorization is crucial if you are to create a secure web application in Flask. Fortunately, Flask allows you to implement authorization in a variety of ways. In this brief guide, the team at Cerbos look at how to implement authorization in a Flask application.

Implementing authorization in a Flask application

The following steps will enable you to implement reliable and secure authorization in your Flask application.

Step 1: Define roles and permissions – The first step in implementing authorization in Flask is to define user roles and associated permissions. Roles typically include “admin”, “user” and “guest” and permissions “read”, “edit” and “delete”.

Step 2: Implement Flask-login – Flask-login is a Flask extension that makes it easier to identify the current user, which is crucial for making authorization decisions.

Step 3: Integrate a user model – Create a model to represent typical users of your Flask app. Customize the user model to include common authentication fields such as username, password, and roles.

Step 4: Implement RBAC – Role-based access control is the process of assigning different roles to different users. Assign the roles you created in Step 1 to the appropriate users.

Step 5: Create custom decorators – Decorators are used to implement authentication checks. Create custom decorators that enforce authorization rules, check permissions and either grant access or redirect to an error page.

Step 6: Account for errors – You will need to create handlers if you are to redirect authorization errors to an error page. Assume any errors are good-faith errors and provide a user-friendly message on the error page.

Step 7: Setup roles and permissions – Store roles and permissions in your database. A common way to do this is to create a table for users and another for roles and then create a join table to associate users with the appropriate roles.

Step 8: Make sure you can update user roles dynamically – There needs to be a mechanism for updating user roles and permissions dynamically either through a dashboard or some sort of admin interface.

Step 9: Test your authorization mechanism – At this point, it is time to test your authorization mechanism. You can do this by writing different test scenarios for different roles, hostile access attempts, successful access and more.

Conclusion

Follow the above steps to implement reliable and secure authorization for your Flask app. Don’t forget to subject your authorization mechanism to regular reviews and to update the mechanism in a timely fashion as user roles and your app’s requirements change.

However, another route to consider is decoupling authorization – therefore averting the many various challenges involved with building your own. If this sounds appealing to you, learn more about Cerbos here.